Blender filter 2D in scene
Use the compositor. Those are all post-render settings that you can apply in the compositor. Here is an example of a simple Gaussian blur (in 2.79 because that's what I have on this computer still. Sorry. ):



You can easily google how to add what ever filter or effect you need by using blender compositor. Using compositor rather than editing the scene to create the same effect can save ages of render time as well. You can do color correction, mist and fog, DOF, vignette, and way more with the compositor.